Electromagnetic motor

ABSTRACT

An electromagnetic motor includes a stator and an armature arranged to move substantially linearly relative to the stator in an intended direction during operation of the motor. A first and second flexure are connected to a first end of the armature. Each flexure has a longest portion which lies substantially in a plane that intersects a plane in which the armature lies at a substantially right angle. The flexures allow motion of the armature in the intended direction while resisting motion of the armature in one or more other degrees of freedom.

BACKGROUND

Referring now to FIG. 1, there is shown a prior art linear motor 10 witha frictionless flexural suspension element 16 from U.S. Pat. No.6,405,599. A stator assembly 12 includes a frame 11 to which a coreportion 13 is mechanically attached. The frame 11 serves as an elementwhich provides convenient coupling of the core portion 13 and otherelements of the linear motor 10. Other embodiments of the statorassembly 12 may not require the frame 11. The frictionless flexuralsuspension system 16 holds an armature 14 in position relative to otherlinear motor elements and controls the motion of the armature 14 and mayexert a restorative force along the axis 17 of the armature 14.

Referring to FIG. 2, there is shown the frame 11, frictionless flexuralsuspension system 16, and armature 14. For clarity, the core portion 13is not shown. The frictionless flexural suspension system 16 includestwo flexure components 46, 48. The ends of components 46, 48 may beattached to the frame 11 by multiple rivets through rivet holes at apressure plate 15. The rivets “sandwich” the flexure components 46, 48between the pressure plate 15 and the frame 11. The flexure components46, 48 flex to allow motion along the axis 17 and may be made ofstainless steel with a thickness of 0.33 mm (0.012 inches). There is asingle flexure component 46, 48 at either end of the armature 14, andeach flexure component has a longest portion which is substantiallyparallel with a longest portion of the other flexure component. Eachflexure 46, 48 is attached to a central portion of an end of thearmature 14.

SUMMARY

In one aspect, an electromagnetic motor includes a stator and anarmature arranged to move substantially linearly relative to the statorin an intended direction during operation of the motor. A first andsecond flexure are connected to a first end of the armature. Eachflexure has a longest portion which lies substantially in a plane thatintersects a plane in which the armature lies at a substantially rightangle. The flexures allow motion of the armature in the intendeddirection while resisting motion of the armature in one or more otherdegrees of freedom.

Embodiments may include one or more of the following features. The motorincludes one or more permanent magnets that are secured to the armature.The longest portion of the first flexure is substantially parallel tothe longest portion of the second flexure. The longest portion of thefirst flexure is skewed relative to the longest portion of the secondflexure. The motor further includes a third flexure connected to thefirst end of the armature, the third flexure (a) having a longestportion which is skewed relative to at least one of the longest portionsof the first and second flexures, and (b) allowing motion of thearmature in the intended direction while resisting motion of thearmature in one or more other degrees of freedom. The motor furtherincludes a fourth flexure connected to the first end of the armature,the fourth flexure (a) having a longest portion which is skewed relativeto at least two of the longest portions of the first through thirdflexures, and (b) allowing motion of the armature in the intendeddirection while resisting motion of the armature in one or more otherdegrees of freedom. The motor further includes a fifth flexure connectedto a second end of the armature, the fifth flexure (a) having a longestportion which is skewed relative to at least one of the longest portionsof the first through fourth flexures, and (b) allowing motion of thearmature in the intended direction while resisting motion of thearmature in one or more other degrees of freedom. The motor furtherincludes a sixth flexure connected to the second end of the armature,the sixth flexure (a) having a longest portion which is skewed relativeto at least one of the longest portions of the first through fifthflexures, and (b) allowing motion of the armature in the intendeddirection while resisting motion of the armature in one or more otherdegrees of freedom. The motor further includes a housing, and eachflexure has two end portions which are connected to the housing and acentral portion which is connected to a first end of the armature.

In another aspect, an electromagnetic motor includes a stator and anarmature having a permanent magnet and arranged to move substantiallylinearly relative to the stator in an intended direction duringoperation of the motor. A first flexure is connected to a first end ofthe armature. A second flexure is connected to a second end of thearmature. The permanent magnet is located between the first and secondflexures. A longest portion of the first flexure is skewed relative to alongest portion of the second flexure. The flexures allow motion of thearmature in the intended direction while resisting motion of thearmature in one or more other degrees of freedom.

Embodiments may include any of the above features and/or the following.The motor further includes a third flexure connected to the first end ofthe armature, the third flexure (a) having a longest portion which isskewed relative to at least one of the longest portions of the first andsecond flexures, and (b) allowing motion of the armature in the intendeddirection while resisting motion of the armature in another degree offreedom. The motor further includes a fourth flexure connected to thefirst end of the armature, the fourth flexure (a) having a longestportion which is skewed relative to at least one of the longest portionsof the first through third flexures, and (b) allowing motion of thearmature in the intended direction while resisting motion of thearmature in another degree of freedom. The motor further includes afifth flexure connected to the first end of the armature, the fifthflexure (a) having a longest portion which is skewed relative to atleast one of the longest portions of the first through fourth flexures,and (b) allowing motion of the armature in the intended direction whileresisting motion of the armature in another degree of freedom. The motorfurther includes a sixth flexure connected to the second end of thearmature, the sixth flexure (a) having a longest portion which is skewedrelative to at least one of the longest portions of the first throughfifth flexures, and (b) allowing motion of the armature in the intendeddirection while resisting motion of the armature in another degree offreedom. The motor further includes a housing, wherein each flexure hastwo end portions which are secured to the housing and a central portionwhich is secured to one of the first and second ends of the armature.

In another aspect, an electromagnetic motor includes a stator and anarmature arranged to move relative to the stator in an intendeddirection during operation of the motor. A first and second flexure areconnected to the armature. The flexures allow motion of the armature inthe intended direction while resisting motion of the armature in one ormore other degrees of freedom. An external load is attachable to thearmature at two corners of the armature.

Embodiments may include any of the above features and/or the following.The motor further includes one or more permanent magnets that aresecured to the armature. A longest portion of the first flexure isskewed relative to a longest portion of the second flexure. The armatureis arranged to move substantially linearly.

In another aspect, an electromagnetic motor includes a stator and anarmature. The stator and armature are arranged for substantially linearmotion relative to each other in an intended direction during operationof the motor. A first and second flexure are connected to a first end ofone of the stator and armature. Each flexure has a longest portion whichlies substantially in a plane that intersects a plane in which thearmature lies at a substantially right angle. The flexures allow motionof one of the stator and armature in the intended direction whileresisting motion of one of the stator and armature in one or more otherdegrees of freedom.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a prior art linear motor;

FIG. 2 is an isometric view of selected elements of the prior art motorassembly of FIG. 1;

FIG. 3 is a perspective view of a linear electromagnetic motor;

FIG. 4 is a partially exploded perspective view of the motor of FIG. 3;

FIG. 5 is a perspective view of the motor of FIG. 3 in which an externalhousing of the motor has been removed;

FIG. 6 is a perspective view of the motor of FIG. 5 in which stator backirons have been removed; and

FIG. 7 is a perspective view of a motor similar to the motor of FIG. 6in which the load plate has been removed and the armature frame has beenmodified.

DETAILED DESCRIPTION

The description below discloses a linear electromagnetic motor in whichtwo pairs of flexural suspension elements (i.e. flexures) are connectedto each end of an armature of the motor. These flexures allowfrictionless movement of the armature in an intended direction of travelwhile providing resistance to movement of the armature in other degreesof freedom (translation, rotation). In some applications of the motor,loading in the transverse (or lateral) directions can be substantial andarbitrary in direction.

With reference to FIG. 3, a linear electromagnetic motor 19 includes ahousing 21. Four flexural suspension elements (i.e. flexures) 23A-D arelocated at one end of the motor 19, and four flexures 25A-D are locatedat the other end of the motor 19. Each flexure is connected to thehousing 21 by riveting both end portions of a particular flexure to thehousing (rivets not shown). For example, the flexure 23A is riveted tothe housing 21 at locations 18 and 20. The ends of the flexures can besecured to the housing 21 in other ways (e.g. bolting, welding). Theseflexures are also connected to an armature of the motor and allowfrictionless movement of the armature in an intended direction of travel(described in further detail below).

The material used for the flexure is selected based on various needs,such as the expected or targeted stress, strain, stiffness (e.g. toprevent the armature from contacting a stator of the motor 19),deflection capability, load handling capacity, number of duty cycles,and operating temperature. Each flexure may be formed from a singlepiece of flexible material, such as metal (e.g. spring steel), plastic(e.g., Dupont Vespel), or composite. In some examples, one materialcriteria for the flexure is that it exhibits high fatigue resistance,e.g., it can withstand a maximum stress over a billion cycles. Highfatigue resistant (100 ksi or greater endurance limit) materialsinclude, stainless steel alloys. Further details of flexures aredisclosed in U.S. Pat. Nos. 6,405,599 and 7,679,229 which areincorporated into the instant application by reference thereto.

Stress, stiffness, size, and linearity are all interrelated in thedesign of flexures for a moving magnet motor. As size is decreased, forexample, the behavior of the flexure (force exerted as a function ofdisplacement) tends to become less linear. Reducing intrinsic stress inthe flexure tends to make the behavior more linear. For a prescribeddisplacement, reducing stiffness allows the flexure to withstand greaterapplied stress. For a given application, i.e., a motor having particularoperating characteristics and packaging constraints, a particularcombination of intrinsic stress, stiffness, size, and linearity in theflexures and the ability to withstand the highest amount of appliedstress can be achieved by varying the shape of the flexure. The flexurescan be formed in several different ways, including stamping or forming,bending using a brake press, and bending with hand tools. The particulartechniques used may depend on the material used and typicalmanufacturing considerations such as capacity, throughput, and qualitycontrol.

Turning to FIG. 4, a cross-support 22 is secured to a first end of anarmature 24 by, for example, rivets (not shown), welding, or aninterference fit (or another suitable attachment method). A set of axes25 is provided for reference. Note that a second end of the armature 24includes a similar cross-support which is not visible in FIG. 4. Bothends of the motor 19 are substantially similar, so only one end will bedescribed. A middle portion 26 of flexure 23A is connected to a portion28 of the cross-support 22. A middle portion 30 of flexure 23B isconnected to a portion 32 of the cross-support 22. A middle portion 34of flexure 23C is connected to a portion 36 of the cross-support 22. Amiddle portion 38 of flexure 23D is connected to a portion 40 of thecross-support 22. Portions 36 and 40 of the cross-support 22 each have apair of through holes for receiving rivets or bolts. In this case,through holes would need to be created in the middle portions 34 and 38of the flexures 23C and 23D. The middle portions of the flexures aresecured to the cross-support by, for example, rivets (not shown), bolts,welding or an epoxy (or another suitable attachment method). Flexures23A-D are thus connected to a first end of the armature 24, and flexures25A-D are connected to a second end of the armature 24. The longestportions of the flexures 23A-D and 25A-D reside in planes substantiallyparallel with each other.

Having a cross-flexure arrangement can make it challenging to connectthe armature 24 to the outer flexure(s) (e.g. 23A, 23B). Splitting theinner flexure into two portions (e.g. 23C, 23D) and providing a gapbetween flexures 23C and 23D allows connection of the armature to theouter flexure(s) while maintaining symmetry (in another example, twoinner flexures such as 23C, 23D can be used with a single outerflexure). This gap allows the portions 28 and 32 of the cross-support 22to extend through this gap. This arrangement enables the flexures 23Aand 23B to be connected to the portions 28 and 32 of the cross-support22. Flexures 23A and 23B are also separated by a gap. The use ofparallel flexures (e.g. 23A and 23B) increases the single axis stiffnessalong the long dimension of the flexures and across the width of theflexures. The cross-flexure arrangement (e.g. flexures 23A and 23C)allows the system to react external loads along two axes (e.g. the Y andZ axes) while allowing motion of the armature along a third axis (e.g.the X axis). Flexures 23A, 23B, 25A and 25B provide high stiffness in adirection parallel to a Z axis. Flexures 23C, 23D, 25C and 25D providehigh stiffness in a direction parallel to a Y axis. The stiffness acrossthe width of a particular flexure is higher than the stiffness along alongest dimension of that flexure. The flexure configuration describedabove provides rotational stiffness against moment loads about axesparallel to the Y and Z axes.

Referring to FIG. 5, the housing of the motor 19 has been removed tofacilitate viewing of the interior of the motor. The flexures 23A-D areback in the same positions as in FIG. 1. A pair of stator back irons 42and 44 provides support for the stator coils of electrically conductivewire 47. The stator back irons are preferably made of a material whichhas high thermal conductivity, thereby facilitating removal of thermalenergy generated in the wire coils. A load plate 49 is secured to thecross-support 22 (e.g. by welding) and thus the armature 24. The loadplate 49 can be connected to an external load (not shown) on which themotor 19 can act.

In FIG. 6 the stator back irons have been removed in order to facilitateviewing of the stator wire coils 47. During operation of the motor 19,magnetic fields from a magnetic assembly 50 that has one or morepermanent magnets interact with the magnetic fields generated by theelectrical current flowing in the stator wire coils 47. This interactioncauses the armature 24 to move substantially linearly back and forthrelative to the housing 21 in an intended direction of movement which issubstantially parallel to the X axis of the coordinate axes system 56. Aload connected to the load plate 49 will likewise be moved back andforth in the same intended direction.

As further shown in FIG. 6, each of the flexures 23A-D and 25A-D has alongest portion which lies substantially in a plane that intersects aplane in which the armature lies at a substantially right angle. Pairsof flexures have longest portions which lie in the same plane and aresubstantially parallel to each other. For example, flexures 23A and 23Bhave longest portions which lie in the same plane and are substantiallyparallel to each other. Each flexure has a longest portion which isskewed relative to a longest portion of four other flexures. Forexample, flexure 23A has a longest portion which is skewed relative to alongest portion of each of flexures 23C, 23D, 25C and 25D. The word“skewed” as used in this application means that a first flexure does notintersect a second flexure and is not parallel with the second flexure.Each flexure has a longest portion which is substantially parallel tothe longest portions of two of the flexures on the opposite end of thearmature (e.g. flexure 23A has a longest portion which is substantiallyparallel with the longest portions of flexures 25A and B). Flexures23A-D and 25A-D allow motion of the armature 24 in the intendeddirection of movement while resisting motion of the armature in one ormore other degrees of freedom (i.e. translation along a directionparallel to the Y and/or Z axes, and/or rotation about axes which areparallel to the X, Y and/or Z axes).

Another example of an armature 58 is disclosed in FIG. 7. The otherelements in FIG. 7 are substantially the same as in FIG. 6 except thatthe load plate 49 has been removed. The armature 58 is similar to thearmature 24 except that the armature 58 has two modified corners 60 and62 which are adapted to have an external load attached thereto. In thisexample there is a through hole at each corner 60 and 62 of the armaturewhich allows the external load to be, for example, bolted to the corners60 and 62. This arrangement attaches the armature to the external loadat locations outside the magnet load path and directly onto a morestructural part of the armature frame.

In another example, the stator coils 47 are attached to the load and thearmature 24 containing the magnet assembly 50 is held in a fixedposition relative to the housing. In this case the coils 47 are alsoconnected to the flexures 23A-D and 25A-D so that the coils can move inthe X direction. This is a moving voice coil motor as opposed to amoving magnet motor which is described above. To summarize, the linearelectro-magnetic motor allows relative motion between the stator and thearmature. In some examples the armature is coupled to the load to causethe load to move linearly, and in other examples the stator is coupledto the load to cause the load to move linearly.

It will be understood that additional modifications may be made withoutdeparting from the spirit and scope of the examples described herein,and, accordingly, other embodiments are within the scope of thefollowing claims.

What is claimed is:
 1. An electromagnetic motor, comprising: a stator;an armature arranged to move substantially linearly relative to thestator in an intended direction during operation of the motor; and afirst and second flexure connected to a first end of the armature, eachflexure having a longest portion which lies substantially in a planethat intersects a plane in which the armature lies at a substantiallyright angle, the flexures allowing motion of the armature in theintended direction while resisting motion of the armature in one or moreother degrees of freedom.
 2. The electromagnetic motor of claim 1,further comprising one or more permanent magnets that are secured to thearmature.
 3. The electromagnetic motor of claim 1, wherein the longestportion of the first flexure is substantially parallel to the longestportion of the second flexure.
 4. The electromagnetic motor of claim 1,wherein the longest portion of the first flexure is skewed relative tothe longest portion of the second flexure.
 5. The electromagnetic motorof claim 1, further comprising a third flexure connected to the firstend of the armature, the third flexure (a) having a longest portionwhich is skewed relative to at least one of the longest portions of thefirst and second flexures, and (b) allowing motion of the armature inthe intended direction while resisting motion of the armature in one ormore other degrees of freedom.
 6. The electromagnetic motor of claim 5,further comprising a fourth flexure connected to the first end of thearmature, the fourth flexure (a) having a longest portion which isskewed relative to at least two of the longest portions of the firstthrough third flexures, and (b) allowing motion of the armature in theintended direction while resisting motion of the armature in one or moreother degrees of freedom.
 7. The electromagnetic motor of claim 6,further comprising a fifth flexure connected to a second end of thearmature, the fifth flexure (a) having a longest portion which is skewedrelative to at least one of the longest portions of the first throughfourth flexures, and (b) allowing motion of the armature in the intendeddirection while resisting motion of the armature in one or more otherdegrees of freedom.
 8. The electromagnetic motor of claim 7, furthercomprising a sixth flexure connected to the second end of the armature,the sixth flexure (a) having a longest portion which is skewed relativeto at least one of the longest portions of the first through fifthflexures, and (b) allowing motion of the armature in the intendeddirection while resisting motion of the armature in one or more otherdegrees of freedom.
 9. The electromagnetic motor of claim 1, furtherincluding a housing, wherein each flexure has two end portions which areconnected to the housing and a central portion which is connected to afirst end of the armature.
 10. An electromagnetic motor, comprising: astator; an armature having a permanent magnet and arranged to movesubstantially linearly relative to the stator in an intended directionduring operation of the motor; a first flexure connected to a first endof the armature; and a second flexure connected to a second end of thearmature, the permanent magnet being located between the first andsecond flexures, a longest portion of the first flexure is skewedrelative to a longest portion of the second flexure, the flexuresallowing motion of the armature in the intended direction whileresisting motion of the armature in one or more other degrees offreedom.
 11. The electromagnetic motor of claim 10, further comprising athird flexure connected to the first end of the armature, the thirdflexure (a) having a longest portion which is skewed relative to atleast one of the longest portions of the first and second flexures, and(b) allowing motion of the armature in the intended direction whileresisting motion of the armature in another degree of freedom.
 12. Theelectromagnetic motor of claim 11, further comprising a fourth flexureconnected to the first end of the armature, the fourth flexure (a)having a longest portion which is skewed relative to at least one of thelongest portions of the first through third flexures, and (b) allowingmotion of the armature in the intended direction while resisting motionof the armature in another degree of freedom.
 13. The electromagneticmotor of claim 12, further comprising a fifth flexure connected to thefirst end of the armature, the fifth flexure (a) having a longestportion which is skewed relative to at least one of the longest portionsof the first through fourth flexures, and (b) allowing motion of thearmature in the intended direction while resisting motion of thearmature in another degree of freedom.
 14. The electromagnetic motor ofclaim 13, further comprising a sixth flexure connected to the second endof the armature, the sixth flexure (a) having a longest portion which isskewed relative to at least one of the longest portions of the firstthrough fifth flexures, and (b) allowing motion of the armature in theintended direction while resisting motion of the armature in anotherdegree of freedom.
 15. The electromagnetic motor of claim 10, furtherincluding a housing, wherein each flexure has two end portions which aresecured to the housing and a central portion which is secured to one ofthe first and second ends of the armature.
 16. An electromagnetic motor,comprising: a stator; an armature arranged to move relative to thestator in an intended direction during operation of the motor; and afirst and second flexure connected to the armature, the flexuresallowing motion of the armature in the intended direction whileresisting motion of the armature in one or more other degrees offreedom, an external load being attachable to the armature at twocorners of the armature.
 17. The electromagnetic motor of claim 16,further comprising one or more permanent magnets that are secured to thearmature.
 18. The electromagnetic motor of claim 16, wherein a longestportion of the first flexure is skewed relative to a longest portion ofthe second flexure.
 19. The electromagnetic motor of claim 16, furthercomprising a third flexure connected to a first end of the armature, thefirst and second flexures also being connected to the first end of thearmature, the third flexure (a) having a longest portion which is skewedrelative to at least one of the longest portions of the first and secondflexures, and (b) allowing motion of the armature in the intendeddirection while resisting motion of the armature in one or more otherdegrees of freedom.
 20. The electromagnetic motor of claim 19, furthercomprising a fourth flexure connected to the first end of the armature,the fourth flexure (a) having a longest portion which is skewed relativeto at least one of the longest portions of the first through thirdflexures, and (b) allowing motion of the armature in the intendeddirection while resisting motion of the armature in one or more otherdegrees of freedom.
 21. The electromagnetic motor of claim 20, furthercomprising a fifth flexure connected to a second end of the armature,the fifth flexure (a) having a longest portion which is skewed relativeto at least one of the longest portions of the first through fourthflexures, and (b) allowing motion of the armature in the intendeddirection while resisting motion of the armature in one or more otherdegrees of freedom.
 22. The electromagnetic motor of claim 21, furthercomprising a sixth flexure connected to the second end of the armature,the sixth flexure (a) having a longest portion which is skewed relativeto at least one of the longest portions of the first through fifthflexures, and (b) allowing motion of the armature in the intendeddirection while resisting motion of the armature in one or more otherdegrees of freedom.
 23. The electromagnetic motor of claim 16, furtherincluding a housing, wherein each flexure has two end portions which aresecured to the housing and a central portion which is secured to a firstend of the armature.
 24. The electromagnetic motor of claim 20, whereinthe armature is arranged to move substantially linearly.
 25. Anelectromagnetic motor, comprising: a stator; an armature, the stator andarmature arranged for substantially linear motion relative to each otherin an intended direction during operation of the motor; and a first andsecond flexure connected to a first end of one of the stator andarmature, each flexure having a longest portion which lies substantiallyin a plane that intersects a plane in which the armature lies at asubstantially right angle, the flexures allowing motion of one of thestator and armature in the intended direction while resisting motion ofone of the stator and armature in one or more other degrees of freedom.